This invention concerns sleeving for encasing and protecting elongated substrates such as wiring harnesses, fuel lines, brake lines and the like subjected to harsh thermal environments.
Elongated substrates, such as wiring harnesses, fluid conduits, such as brake lines and fuel lines, and optical fiber bundles, are often used in automotive, aerospace and marine applications where they are subjected to intense heat. Wiring harnesses and fuel lines routed through an enclosed engine compartment, for example, in an automobile, boat or aircraft, are subjected to both radiant and convective heat from the engine, particularly the exhaust manifold. Similarly, fuel lines and wiring in the vicinity of a rocket engine nozzle or on an orbiting satellite, exposed to direct sunlight in the vacuum of space, require thermal protection to ensure proper and continued operation.
Thermal protection has been afforded by the use of composite protective sleeving comprising a layer of woven glass fiber bonded to a layer of reflective metal foil. Flat sheets of the composite are reverse folded with the reflective metal foil layer facing outwardly. Opposite edges of the sheets are positioned adjacent to one another and sewn together forming a longitudinal seam.
While such sleeving provides thermal protection, it is relatively expensive and time consuming to manufacture, largely due to the sewn longitudinal seam. Furthermore, such a seam inevitably leaves layers beneath the reflective layer, such as the glass fiber layer, exposed to the thermal environment. The exposed layers compromise the thermal shielding otherwise afforded by sewn sleeves and allow a relatively hot region to form along the substrate within the sleeve. Additionally, the reverse fold results in a lengthwise crease along the sleeve which significantly weakens the glass fiber layer, decreasing its tear strength by as much as 75% and, thus, providing a failure initiation point on the sleeve. There is clearly a need for a thermal protective sleeve which avoids the disadvantages of the sewn sleeve and which can be produced more rapidly without the need for sewing.
The invention concerns an insulative, flexible sleeve for protecting elongated substrates subjected to harsh thermal environments. The sleeve is formed from a composite sheet comprising a metallic reflective layer, a reinforcing layer and an insulative layer.
The metallic reflective layer is preferably aluminum, either in the form of a thin foil adhered to the reinforcing layer or as a vacuum deposited coating. Preferably the reinforcing layer comprises a flexible, tear-resistant polyester sheet material such as MYLAR(copyright) that substantially overlies the reflective layer. The insulative layer comprises a fibrous, non-woven material, preferably a thermoplastic felt having a predetermined thickness providing air spaces for increased insulative capability. The insulative layer substantially overlies and is attached to the reinforcing layer, preferably using adhesive.
Upon forming the layers into a composite sheet, a reverse fold is formed between a first and a second portion of the sheet so as to bring the first sheet portion into overlying relation with the second sheet portion. The fold places the insulative layer on the first sheet portion in facing relation with the insulative layer on the second sheet portion, the reflective layer faces outwardly. A seam is formed between the first and second sheet portions attaching them together. Preferably, the seam is formed by fusing the facing insulative layers on the first and second sheet portions together using ultrasonic welding techniques. The seam is positioned along the sheet in spaced relation to the reverse fold. Together, the first and second sheet portions, the reverse fold and the seam define a central space therebetween adapted to receive elongated substrates to be insulated.
It is an object of the invention to provide a thermally insulative sleeve for elongated substrates.
It is another object of the invention to provide a sleeve insulating against all modes of heat transfer.
It is again another object of the invention to provide a sleeve having a non-woven insulative layer.
It is yet another object of the invention to provide a sleeve formable by welding the insulative layer to itself to form a seam.
It is still another object of the invention to provide a sleeve wherein the welding is performed by ultrasonic welding techniques.
These and other objects and advantages of the invention will become apparent upon consideration of the following drawings and detailed description of preferred embodiments.